1. Field of the Disclosure
The present disclosure relates to a machining tool for machining the surface of an attrition liner that may be provided radially outward of a set of fan blades in a gas turbine engine.
2. Description of the Related Art
An attrition liner in a gas turbine engine may be provided around the fan blades with a small gap between the fan blade tip and the attrition liner. Minimising the gap may minimise over-tip leakage and thus maximise aerodynamic performance of the fan blades. In order to minimise the gap between the fan blade tip and the attrition liner, the attrition liner may be thicker than required at installation and then machined to the required thickness as part of the installation process.
It should be appreciated that the present disclosure may be applicable to circumstances in which a single section of attrition liner is being replaced. In such an arrangement, the new section of attrition liner may be machined until it has the same thickness as the sections of the attrition liner on either side that are to be retained. The present disclosure may also relate to circumstances in which the entire attrition liner, namely corresponding to the complete circumference of the fan case around the fan blades, is to be replaced. This may occur, for example, when an engine is first installed or during a major engine overhaul.
The previously known arrangements for machining newly installed attrition liners or sections of attrition liners may have drawbacks. For example, in particular for the replacement of a single section of attrition liner, it is known to machine the attrition liner to the desired thickness using a hand-held machining tool. However, such an arrangement requires a highly skilled operator to produce the required shape. Alternatively or additionally, the process may produce a large amount of dust that poses a health and safety risk to the operator. Alternatively or additionally, the process may require the operator to be in an uncomfortable position, for example kneeling, for up to four hours in order to machine a single section of the attrition liner. If the section of attrition liner to be replaced is around the top dead center of the fan case, the process may be very difficult to carry out.
For the machining of an entire attrition liner, it is known to provide dedicated tooling. However, the known equipment is heavy and is therefore a large floor-standing piece of equipment to provide stability. It may be centred on the low pressure compressor shaft and then cuts the attrition liner to a pre-set depth. However, such equipment is very large and relatively expensive. Accordingly, it may only be stationed at an engine overhaul facility. Furthermore, for the known equipment to be centralised on the low pressure compressor shaft, it requires the removal of the low pressure compressor fan disk, namely the fan blade mount that rotates on the low pressure compressor shaft. This may undesirable because once the low pressure compressor disk is removed, there is a risk of the mating faces of the low pressure compressor disk and the low pressure compressor shaft starting to corrode.